(Sorry, typo in previous email. Please read that as) I have another question: why is any given operation implemented twice for the same architecture?
Ref: opal/asm/base/AMD64.asm and opal/include/opal/sys/amd64/atomic.h, say function opal_atomic_cmpset_32() Thanks! On Fri, Apr 1, 2016 at 2:26 PM, Sreenidhi Bharathkar Ramesh < sreenidhi-bharathkar.ram...@broadcom.com> wrote: > Hi Paul, > > Thanks for the response, I understand. > > I have another question: why is any given operation implemented twice for > the same architecture? > > Ref: opal/asm/base/ARM.asm and opal/include/opal/sys/amd64/atomic.h > > Please let me know. > > Thanks, > - Sreenidhi. > > > > On Thu, Mar 31, 2016 at 2:28 AM, Paul Hargrove <phhargr...@lbl.gov> wrote: > >> Sreenihdi, >> >> Maintenance of the "other" files is, at least, required for older >> compilers (including several non-GNU ones) which have support for GCC >> inline ASM constructs but do not include the __sync functions. >> >> Additionally, the __sync functions always include a full memory fence >> while there are places where Open MPI only needs Acquire or Release. In >> that sense the use of the GCC builtin atomics is not always an >> "optimization". >> >> -Paul >> >> On Wed, Mar 30, 2016 at 4:19 AM, Sreenidhi Bharathkar Ramesh < >> sreenidhi-bharathkar.ram...@broadcom.com> wrote: >> >>> Hello, >>> >>> I did few more experiments. Built-in atomics are disabled by default >>> and can be enabled by "--enable-builtin-atomics". With this option, a >>> different atomic file is include (I mean, different from the other three >>> mentioned in the earlier email). >>> >>> opal/include/opal/sys/sync_builtin/atomic.h >>> >>> By enabling "--enable-builtin-atomics", the OpenMPI library will not >>> only get the latest optimizations from GCC __sync functions, but also get >>> all additional functions, such as <__sync_or_and_fetch> < >>> __sync_and_and_fetch> etc. Also, this way, the arch/*.asm files need >>> not be maintained. >>> >>> Seems there is more of an advantage to have "--enable-builtin-atomics". >>> Am I missing something ? Please let me know your thoughts. >>> >>> Thanks, >>> - Sreenidhi. >>> >>> On Wed, Mar 30, 2016 at 10:33 AM, Sreenidhi Bharathkar Ramesh < >>> sreenidhi-bharathkar.ram...@broadcom.com> wrote: >>> >>>> Hello, >>>> >>>> With respect to atomic operations in assembly, I can see three source >>>> files, for the same AMD64 architecture. >>>> >>>> 1. opal/asm/base/AMD64.asm >>>> 2. opal/include/opal/sys/amd64/atomic.h >>>> 3. opal/include/opal/sys/atomic_impl.h >>>> >>>> What is the need for three files ? How are they inter-related ? >>>> >>>> Please let me know. >>>> >>>> Thanks, >>>> - Sreenidhi. >>>> >>> >>> >>> _______________________________________________ >>> devel mailing list >>> de...@open-mpi.org >>> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel >>> Link to this post: >>> http://www.open-mpi.org/community/lists/devel/2016/03/18733.php >>> >> >> >> >> -- >> Paul H. Hargrove phhargr...@lbl.gov >> Computer Languages & Systems Software (CLaSS) Group >> Computer Science Department Tel: +1-510-495-2352 >> Lawrence Berkeley National Laboratory Fax: +1-510-486-6900 >> >> _______________________________________________ >> devel mailing list >> de...@open-mpi.org >> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel >> Link to this post: >> http://www.open-mpi.org/community/lists/devel/2016/03/18734.php >> > >
